Here's a brewing irony for Senate Republicans: If they have a near-perfect run in 2018 races, they could get close to the coveted filibuster-proof majority of 60 out of 100 seats.

There are 10 Senate Democrats running for reelection in states President Trump won, while Republicans, who currently have a 52-seat majority, only have one or two vulnerable candidates.


But Republicans have struggled to recruit top candidates in these Trump states. A lack of a clear leader is leading to a bunch of lower-tier candidates jumping into the race, which means Republicans could spend the next year in potentially expensive (and, in some cases, divisive) primaries in some key states.

This isn't the end of the world, but it's not a perfect start for a perfect run for Republicans.

It's a trend we noticed in April that is still going on today, with news that Rep. Ann Wagner (R-Mo.) will not challenge one of the Democrats' most vulnerable senators up for reelection in 2018, Claire McCaskill (Mo.).

A similar dynamic is playing out in these Trump states where Senate Democrats are trying to win reelection next year, such as:

In Wisconsin, Rep. Sean P. Duffy (R) decided not to run to challenge Sen. Tammy Baldwin (D). There are at least six possible GOP candidates who could try to challenge Baldwin.

In Indiana, Rep. Susan Brooks (R) decided not to run against Sen. Joe Donnelly (D), possibly the most vulnerable Senate Democrat. Her colleagues, GOP Reps. Luke Messer and Todd Rokita, do look like they'll run, and they've already started attacking each other in pretty dramatic ways, like accusing the other of planting negative stories or making “unhinged” comments.

In Pennsylvania, Rep. Patrick Meehan (R) decided not to run against two-term Sen. Robert P. Casey Jr. (D). Now there are at least four Republicans who have launched campaigns, from state representatives to a real estate developer and an energy executive. Pennsylvania Republicans tell National Journal they'd feel better about the race if either U.S. Reps. Lou Barletta or Mike Kelly decided to run. (Both have said they're thinking about it.)

In West Virginia, a state Trump won by more than 40 (!) points, U.S. GOP Rep. Evan Jenkins is running to try to unseat Sen. Joe Manchin III (D). But a super PAC recently jumped into the race in favor of likely GOP candidate Attorney General Patrick Morrisey and attacked Jenkins as a Manchin “mini me.”

In Ohio, state Treasurer Josh Mandel (R) is the leading candidate to challenge two-term Sen. Sherrod Brown (D). But a wealthy investment banker and GOP donor decided to run, too.

And Montana Republicans lost their top recruit, Ryan Zinke, after Trump picked him to be his interior secretary. Attorney General Tim Fox (R) also said no thanks to challenging two-term Sen. Jon Tester (D), which has left the state auditor as the biggest name among half a dozen potential candidates.

Finally, in North Dakota, Republicans don't have a candidate yet to challenge Sen. Heidi Heitkamp (D), another state Trump won by double digits (20 points).

Basically, Democratic operatives point out, there are Republican primaries in nearly every competitive Senate race right now.

What's going on here? A few things:

In many of these states, if the Democrat could be unseated, it's possible Republicans could hold the seat for a long time. And the more likely your party is to win a race, the more likely on-the-fence candidates are to jump in.

But that doesn't explain why some top recruits in these states said “no.” Everyone has different reasons (Duffy in Wisconsin has eight kids, Zinke in Montana took a Cabinet appointment instead). But if any of these races were an easy win, you'd think more experienced politicians would say “yes” to getting in.

That more haven't suggests:

1) It's not going to be as easy as the numbers suggest to take down some of these Senate Democrats, many of whom won tough races in 2012 in red-leaning states and have been in office for almost a dozen years.

2) There could be a Trump factor weighing heavily against Republicans' calculations. History tells us the party in power generally loses seats in the next congressional midterm; more so if the president is unpopular. And pretty much since he took office, Trump has been the least-popular president in modern times.

3) The longer Republicans in Congress go without a legislative win, the harder it is for them to sell their candidacy on a state level. Republicans need to pass a health-care bill they can sell. They'd like to get tax reform done, too. Right now, they have not done any of that.

4) A few closer-than-expected special elections in Georgia, Kansas and Montana for Republicans raise the possibility that the Democrats' base is fired up in a way it wasn't in past congressional elections. (Though Republicans won all of the elections.)

November 2018 is still a year-and-a-half away, so there's no rule that Senate candidates have to get in right now. And primaries aren't the end of the world; sometimes they make the candidates who emerge stronger.

Plus, Republicans argue, Democrats don't have especially stellar recruits in their two key races. U.S. Rep. Jacky Rosen (D-Nev.) just won a congressional seat in Nevada and is going to challenge Republican Sen. Dean Heller, but that doesn't preclude others from getting in. Democrats have no one in Arizona to challenge Republican Sen. Jeff Flake.

But since we're going to spend the next 489 days trying to assess which opposing force is stronger in the 2018 Senate midterms — Senate Democrats' vulnerability in Trump states or Trump's unpopularity — let's plant an early flag and say that, so far, Trump's unpopularity appears to be weighing on Senate Republicans.