NASHVILLE, Tenn. (AP) — President Donald Trump on Tuesday resumed his efforts to build a stable of Republicans who will promote his agenda and serve as a check on Democrats aiming to regain control of the House or Senate — if not both.

Trump traveled to Nashville, Tennessee, to raise campaign cash for Republican Rep. Marsha Blackburn, who's running for a Senate seat, and to headline a rally with his most loyal supporters.

Trump said, "We need Marsha in the Senate to continue the amazing progress and work" of his first 16 months in office. "To keep on winning, you have to vote Republican in November."

Blackburn is expected to face Democratic former Gov. Phil Bredesen to replace Republican Sen. Bob Corker, who is retiring. The Tennessee campaign is among several races crucial to Trump's plans to maintain control of the Senate, where Republicans are defending a narrow two-seat majority.

Trump criticized Bredesen for being backed by national Democrats, including the Senate and House leaders.

"He's a tool of Chuck Schumer and of course the MS-13 lover Nancy Pelosi," Trump said.

The House Democratic Leader criticized Trump earlier this month after he called members of the international gang "animals."

Trump added that Bredesen donated to Hillary Clinton's presidential campaign in 2016, saying, "Phil Bredesen supported her and he supported her ideas."

Trump plans a series of political rallies and events in the coming months to boost Republicans and brand Democrats as obstructionists to his agenda. The president held a similar rally in Indiana earlier this month, appearing with Republican businessman Mike Braun and ripping Democratic Sen. Joe Donnelly as a "swamp person" who refused to aid the GOP agenda.

Trump is using the campaign appearances to mobilize his core backers by his highlighting accomplishments in office, like improving economic indicators and moving the U.S. embassy in Israel to Jerusalem, and resurrecting some of his go-to lines from the 2016 campaign.

"I don't want to cause a problem, but in the end, Mexico's gonna pay for the wall," Trump said of his signature campaign promise.

Mexico has tirelessly objected to the notion that it would pay for the border wall — for which Trump has sought billions from Congress — and Trump's talk on the matter has strained relations between the two countries.

Earlier Tuesday, Trump raised the prospect of special counsel Robert Mueller's Russia probe affecting the November elections and blamed Democrats for "Collusion." On Twitter, he said the "13 Angry Democrats" on Mueller's team "will be MEDDLING with the mid-term elections, especially now that Republicans (stay tough!) are taking the lead in Polls." Mueller is a Republican.

Beyond Indiana, Trump has used his Twitter page to boost California Republican gubernatorial candidate John Cox, hoping to strengthen the party's chances of securing a spot on the ballot in November. He has also set his sights on Montana, where Democratic Sen. Jon Tester is seeking re-election in a state Trump carried in a landslide. Both states have primaries on June 5.

The president is raising money later in the week in Texas to benefit Senate Republicans and his 2020 re-election campaign.

Tennessee has a history of electing centrist senators and the race could be complicated by Corker's up-and-down relationship with Trump. Corker once said Trump had turned the White House into an "adult day care center" and the president tweeted that Corker "couldn't get elected dog catcher in Tennessee."

Yet Corker was in the Oval Office on Saturday, receiving praise from the president for his help in securing the release of an American imprisoned in Venezuela. The breakthrough happened after Corker held a surprise meeting in Caracas with Venezuelan President Nicolas Maduro. Corker also greeted Trump at the Nashville airport Tuesday, joined by Blackburn and Sen. Lamar Alexander, R-Tenn., among other dignitaries.

Corker has called Bredesen a friend and said he won't actively campaign against him.

Trump, meanwhile, offered an early endorsement of Blackburn in April, tweeting that she is "a wonderful woman who has always been there when we have needed her. Great on the Military, Border Security and Crime."

Blackburn, who served on Trump's transition team, has embraced the president and called herself a "hardcore, card-carrying Tennessee conservative."

Bredesen, who is attempting to become the first Democrat to win a Senate campaign in Tennessee since Al Gore in 1990, has aired TV ads in which he says that he's "not running against Donald Trump" and that he learned long ago to "separate the message from the messenger."

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