The Senate GOP is betting the ranch that President Trump can deliver a bigger Senate majority in the 2018 midterm election.  Burgess Everett and Kevin Robillard at politico.com report that "Trump will be front and center in every state that helped elect the president," campaigning against the Democrat incumbents who are "hindering his agenda":

Republicans will lean most heavily on Trump in five deeply conservative states where the president remains highly popular and where he crushed Hillary Clinton: West Virginia, North Dakota, Indiana, Missouri and Montana.  But they say they will also deploy Trump in the next tier of swing states that Trump won more narrowly: Ohio, Pennsylvania, Michigan, Wisconsin and Florida.

Senate GOP strategists think, with the Democratic base already "motivated to vote," that the Republicans will need Trump on the campaign trail to "fire up their base, too":

Base mobilization is absolutely essential for victory, and there is absolutely no one better at energizing the GOP base than President Donald Trump.

The politico.com piece points out that the president's campaigning for Rick Saccone in Pennsylvania and Roy Moore in Alabama did not lead to Republican victories, but both of those races were arguably problematic in many ways for the Republicans.  In addition, neither of the winning Democrats, Conor Lamb in Pennsylvania and Doug Jones in Alabama, had a voting record to run against.

In contrast, the ten Democratic Senate incumbents running in states that Trump won have long voting records to run against, and their voting records are not pretty for Trump-supporters. 

While the red-state Democrat senators up for election like to portray themselves as moderates, there is little or no daylight on the big issues between their votes and the votes of Bernie Sanders, Elizabeth Warren, Kamala Harris, and Corey Booker, to name a few of the most left-leaning Democrats in the Senate.

On the 2017 GOP tax cuts, a cornerstone of the Trump agenda, the ten Trump-state Democrat incumbent senators voted in lockstep with Sanders and Warren against.  Not one of them strayed from Chuck Schumer's party-line resistance to help their tax-paying constituents and fuel the job-creating economic boom.

On Obamacare repeal, our ten Democrats never strayed from the Democrats' party line on resisting all three versions voted on in the Senate, choosing instead to defend their party's broken health care promises no matter the cost.

On Judge Gorsuch, only Heidi Heitkamp of North Dakota, Joe Manchin of West Virginia, and Joe Donnelly of Indiana voted yes.  The other seven of our Democrat incumbents voted with the Sanders-Warren wing against the nomination of Judge Gorsuch. 

On President Trump's administration nominees, all but Heitkamp and Manchin voted with Sanders and Warren against Trump's key nominees for attorney general, secretary of state, treasury secretary, HHS secretary, education secretary, OMB director, and EPA administrator. 

Everett and Robillard add that there was "scant Democratic support" for Trump's "rollbacks of Obama-era regulations," which have been a major factor in the Trump economic boom.

Trump has already begun campaigning in Missouri.  Missouri attorney general Josh Hawley, the "front-runner for the Republican nomination to challenge" Missouri's incumbent senator, Claire McCaskill, highlighted McCaskill's party-line tax cut opposition when the president made his third visit to the state last week:

The Hawley campaign hit Ms. McCaskill for siding with Senate Majority Leader Charles E. Schumer, New York Democrat, to oppose tax relief for Missourians, reminding voters that she dismissed the tax cut benefits for workers as "scraps" when voting against it in December.

While the politico.com piece notes that Trump has relatively good relationships with Heitkamp and Manchin, the writers add that "Trump will be plenty motivated to take on those Democrats because they have opposed so much of his agenda," quoting Montana Republican senator Steve Daines:

He's learned his lesson. Trump thought there was going to be bipartisan support?  Not happening.  Supreme Court, [deregulation], circuit judges, tax bill – that's a pretty long list.

The politico.com writers contend that having Trump out on the trail will provide "non-stop news coverage" and "alleviate" one of the Republicans' "biggest fears for 2018: that a depressed base will allow Democrats to run roughshod over them even in heavily conservative areas."  

The writers then make the curious claim that Trump's campaigning will remind voters that "Democratic moderates will be a more effective check on the president" than a Republican replacement would be.  By that logic, red-state voters would re-elect Democrat party-line incumbents, thereby serving as a check on a president those same voters elected by large margins.  In other words, red-state voters would vote against their own interests.

Democratic senatorial incumbents in Trump states who put zero daylight between their votes and the votes of the Sanders-Warren wing of the party on the issues most important to Trump voters will be hard pressed to defend their records when the president comes calling on the campaign trail in their states.