Republicans eyeing fall's midterm elections have some things to feel good about for the first time in months: President Donald Trump's numbers are up, their generic ballot deficit is down, and a growing economy lets them talk about something other than the tweets out of the White House.

It doesn’t mean the GOP is on track to stave off deep losses in November — just that those defeats no longer appear as inevitable as they once did.

"I'm more bullish than I've been the entire cycle," said California-based GOP strategist Jason Cabel Roe, pointing to the GOP-passed tax bill, in an interview last week. "They're going to look past whatever complaints they have with things happening in the White House or Washington, and focus more on how it affects their household bottom line."

It’s just the latest twist in an already long political cycle, one that began with serious questions about Democrats’ ability to channel grassroots energy into actual votes and finished last year with a despondent GOP wondering how it lost big races in Virginia and deep-red Alabama.

Nine months before the midterms, top strategists on both sides of the aisle are struggling with the volatility of the political environment, but agree that a few core dynamics are driving the campaign trajectory: Trump’s approval rating—and that of his tax law—are ticking up, the left is energized but will face a series of divisive primaries, and a spate of recent GOP retirements tilts in the Democrats' favor.

Here is McClatchy’s look at where the most important mechanics of the midterms environment stand today, based on conversations with more than a dozen top political strategists.

Is economic growth a bulwark against progressive enthusiasm?

Republicans who have long worried about the potential for a midterms wipeout are now expressing cautious optimism that improving views of the signature Republican tax reform measure, as well as a strong economy, will help mitigate the myriad challenges confronting the GOP. The tax bill, passed late last year, has also energized the GOP base.

"This tax cut has been huge," said Beth Campbell, the Republican national committeewoman from Tennessee. "Huge."

Of course, there's no guarantee that the economy will still be humming in October, and just Monday, the Dow Jones Industrial Average plummeted. Yet even if the overall economic picture is strong, there is concern among some Republicans that Trump--and his polarizing Twitter feed—will knock GOP candidates off message and overshadow the tangible accomplishments they're hoping to tout.

Meanwhile, progressive activists are motivated, turning out for top-of-the-ticket races in Virginia and Alabama as well as for local races up and down the ballot and across the country. No one knows just how many will show up in key races come November.

"We better be out there, definitely, selling the benefits of some of the good things that are happening, but we acknowledge that the left is energized right now," said Tim Phillips, the president of the major conservative organization Americans for Prosperity, speaking to reporters at a recent gathering of the influential Koch brothers’ political network. "No question about that. It's not just marches and such that they're doing. It's showing in some of the recent elections."

Democratic primaries complicate the party’s path to a majority

Democrats are delighted by a surge of candidates in 2018, happy to field credible contenders in places where until recently the party struggled to even compete.

But the abundance of candidates has also caused a logjam in dozens of key battlegrounds, raising the possibility that the best candidate—or even the second or third best candidate—might not make it to the general election. Compounding concern among some Democrats is the possibility that a hyper-competitive primary will drag the eventual nominee to the left on key policy questions that could come back to bite them in the general.

The concern is especially acute in California (host to more than a half-dozen battleground House races), where election rules stipulate that the top two vote-getters in the primary move on to the general election regardless of party. Especially in open-seat races, that means four or five Democratic candidates could split the vote to such a degree that a pair of Republican candidates could advance, even in a Democratic-leaning district.

Democrats say party leaders and the DCCC are doing their best to mitigate the possible damage.

“They’re cognizant of that, and in their mind, they’d like to narrow the field,” said one California Democrat strategist. “But there’s only so much they can do, right?”

Still, Democrats say they’ve been pleased with how many primaries have developed, with the candidates thus far saving most of their ire for Trump and resisting a wholesale shift to the left.

“Whichever candidate comes out of the primaries will be a good Democratic candidate,” said Brian Smoot, a former political director for the DCCC. “The fact so many of them are interested in running leads me to believe there’s a lot of opportunities for Democrats on Election Day.”

Retirements and redistricting scramble the landscape

A string of influential Republican lawmakers have announced retirement, setting up many open-seat contests that appear challenging for the GOP to defend.

From Rep. Ileana Ros-Lehtinen’s Miami-area seat, to House Foreign Affairs Committee Chairman Ed Royce’s Orange County, Calif. district, Democrats see pick-up opportunities in seats that were, until now, held by strong GOP incumbents.

“There’s been a lot of retirements,” said former Pennsylvania GOP Chairman Rob Gleason, when asked how concerned the Republican National Committee should be about midterms. “It’s hard to replace incumbents. That always gives you an opportunity, whether Republican or Democrat, and they should be very concerned about it.”

Meanwhile, several states—most prominently, Pennsylvania—are grappling with redistricting issues that inject a degree of uncertainty into what the ultimate congressional maps could look like, and another layer of uncertainty into the midterms environment as 2018 barrels on toward Election Day

Which party has a cash advantage?

On the surface, Democrats look as if they have a big financial edge. More than 30 GOP incumbents were outraised by at least one Democratic challenger last fundraising quarter, while the DCCC’s own fundraising continues to outpace GOP counterparts.

The party will also benefit from an unusual influx of progressive grassroots cash. One group, Swing Left, with the help of liberal organizations such Daily Kos Elections, has already raised $4 million for a fund that will contribute to the eventual Democratic nominees in more than 70 battleground districts — an unprecedented effort that could provide a lifeline of support to Democratic candidates in the days after they win their primaries. The group’s goal is to raise $7 million, which if met, would mean it would distribute roughly $100,000 to each candidate.

“We think it can be a big difference-maker,” Ethan Todras-Whitehill, the group’s executive director and co-founder.

Still, Democrats are worried that well-moneyed groups on the right could dent, or even erase, their financial edge. The political network of Charles and David Koch last week promised to spend $400 million on politics and policy through the midterm elections, cash that could be buffeted by spending from organizations such as the Chamber of Commerce or Ending Spending.

“Ultimately, as we head into the 2018 midterms, I’m confident that a blue wave is building,” Jesse Ferguson, veteran Democratic strategist, wrote in USA Today this week. “But I’m left wondering: Is our surfboard big enough?”