He may not be on the ballot in November, but with 100 days to go before the midterms, the critical race for control of Congress has become all about President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE.

Midterms have traditionally been referendums on the president and the party in power, but Trump has had an influence over this year’s race in a way that strategists say they have never seen before. And that could be a double-edged sword — for both Democrats and Republicans.

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Republicans have hitched themselves completely to the president, making primaries a competition over who can sound and act most like Trump. But with Trump’s approval rating stuck in the mid-40s, that loyalty to the president could backfire should his numbers not start improving soon.

For Democrats, opposition to Trump has fired up the base in primaries across the country. But strategists worry it could drown out more winning messages such as improving health care, especially if the anti-Trump base forces Democratic candidates into potentially controversial positions like calling to impeach the president.

“The most difficult thing I’ve found in races at every level are people having any interest in any of it other than talking about the president,” said Adam Goodman, a GOP strategist in Florida.

“I've never seen a time in my career where everything and anything emanates from one place and one person.”

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The stakes are especially high for Republicans, given that the party in power has historically lost seats in both the House and Senate during the midterms.

Trump’s numbers remain underwater, with the average of polls tracked by RealClearPolitics showing the president with an approval rating of about 43 percent.

Strategists and political observers say those ratings would need to improve fast to increase the prospects of Republicans in midterms, especially in the House.

In 2010, former President Obama’s rating was at around 45 percent, below the “magic number” of 46 percent that Republicans believed would give them the House, according to Doug Heye, who was the communications director for the Republican National Committee.

Democrats are already aggressively targeting all 25 GOP-held seats that Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE won in 2016, while also wading into GOP-leaning swing seats and even some deep-red seats. Democrats believe the number of seats at play for them could exceed 100, way more than the 23 seats they need to flip to take over the House.

Democrats see special opportunities in suburban seats where polls show weak favorability ratings for Trump, and plan to turn out women, especially minority women — a game plan that helped propel Democrats to victory in the governor race won by Ralph Northam (D) in Virginia and Doug Jones’s (D) stunning win in the Senate special election in Alabama.

Trump’s impact could be more favorable for Republicans in the Senate since 10 Democratic incumbents are up for reelection in states the president won in 2016 — with five of those by double digits.

The president still remains popular in states like West Virginia, North Dakota, Missouri and Montana, which also hold marquee Senate races. Trump has already made a number of campaign stops in these states and has upcoming rallies in Florida and Pennsylvania, both states the president won narrowly.

Trump could come to haunt Republicans in other ways as well — by undercutting what should be winning issues in the shape of an improving economy and a surge in job creation.

Estimates on Friday showed the U.S. economy expanding at a 4.1 percent rate in the April-June quarter, the fastest pace since the third quarter of 2014.

GOP strategists say Republicans should be taking credit for that and campaigning on the tax cuts signed into law late last year, depriving Democrats of the chance to frame that action as a giveaway to billionaires and corporations.

Yet to the frustration of many Republicans, the good news on the economy keeps getting drowned out by Trump himself and his penchant for generating negative headlines, including after his performance at a summit with Russian President Vladimir Putin.

Republicans also cite frustration with the president’s frequent tweets railing against special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s probe into Russia’s election meddling and his public spats with foreign leaders as unhelpful to their cause.

“The economy and tax reform isn’t an abstract issue like Russia. I wish the president would talk every day about the economy and tax reform instead of other things he talks about,” said Ryan Williams, a former adviser on Mitt Romney Willard (Mitt) Mitt RomneyTrump 'no longer angry' at Romney because of Supreme Court stance GOP lawmakers distance themselves from Trump comments on transfer of power McConnell pushes back on Trump: 'There will be an orderly transition' MORE’s (R) 2012 presidential campaign.

The stakes are equally high for Democrats. The president has been a rallying force in primaries, and Democrats believe they can campaign as a check on Trump and a Republican Congress.

Unpopular presidents have been a winning issue for both parties in the past. In 2006, Democrats campaigned against deeply unpopular President George W. Bush to take over the House by winning 31 seats. And in 2010, Republicans used opposition to ObamaCare, and Obama more broadly, to win a stunning 63 seats to regain the House.

But some Democrats also believe that campaigning on an anti-Trump message alone will not be enough to hand them Congress, especially as a fired-up base calls for positions many leaders find uncomfortable, such as impeaching the president or abolishing Immigration and Customs Enforcement.

Strategists say Democrats will need to expand their message to avoid a repeat of 2016, when Democratic candidate Hillary Clinton sought to make the election all about Trump, only to go on to lose in one of the biggest upsets in U.S. political history.

“There was extreme anger towards Trump leading into 2016, that didn’t cross the line electorally, so Democrats certainly need something to galvanize for Democrats, not just against,” said Kevin Cate, a Democratic strategist in Florida who worked on Obama’s 2008 campaign.

These strategists say Democrats have an especially winning issue in health care. In fact, ObamaCare, and popular provisions like coverage for those with pre-existing conditions, have become winning issues for Democrats, unlike in 2010, these strategists say.

Yet whether Democrats can use that opportunity remains very much in doubt, especially as Trump continues to suck up all the coverage.

“Our candidates are not going to lead with talking about Trump,” said Washington Gov. Jay Inslee (D). “They’re going to lead by talking about economic growth and improving education. You don’t have to mention Trump very much.”

Reid Wilson contributed to this report.