Mitch McConnell can always be counted on to put a brave face on things. Asked on CNN's State of the Union on Sunday whether he's encouraging Republican Senate candidates to distance themselves from Donald Trump should he be the party's nominee, McConnell essentially said that it isn't a problem. "We are going to run individual races no matter who the presidential nominee is," McConnell said. "Senate races are statewide races. You can craft your own message for your own people. And that's exactly what we intend to do this fall, no matter who the nominee is."

It's certainly what many of them will try to do. But can they get away with it?

A few might. But distancing yourself from your party's leader may be harder now than it has ever been.

To see why, we have to start with an understanding of how much information voters have about different candidates. We can think about a kind of information hierarchy, the top of which is the presidential race. That contest will dominate all the news sources people have about politics: newspapers, local and national TV news, social media, even the conversations they have with family, friends, and co-workers. If the race is between Trump and Hillary Clinton, the clash of these two big, controversial personalities will dominate the news.

The next level down is races for Senate or governor — amply funded, and featuring incumbents with whom people have at least a passing familiarity, but not nearly as prominent as the presidential race. You'll absolutely hear Trump and Clinton's messages, whether you believe them or not, but with the lower offices, it's a challenge just to get the candidate's name and face in front of people. Go to House seats, and then farther to state legislature or local races, and voters hear only the occasional snippet, drowned out by everything else that's going on.

That means that it can be difficult to convince voters of something a bit complicated, something that requires them to undo their default assumptions. And one of those assumptions is that candidates from the same party are going to be partners.

Split-ticket voting (choosing one party's candidate for president and a different party's candidate for lower offices) has declined in recent years, which is understandable in an era of partisan polarization and tight party unity. Half a century ago, when both parties contained a relatively broad ideological spectrum — for instance, the Democratic Party had both Northern liberals and Southern conservatives — it made more sense to view an individual senator or congressman as a free agent who might act independently of his or her party. But today, most important votes break firmly along partisan lines, which means that your senator is probably not going to surprise you, or the president, with anything he or she does.

That's not to say there are no more maverick legislators who frequently abandon their party to support the other side's position. There are a few, like Joe Manchin (D-W.Va.) or Susan Collins (R-Maine). But there are fewer of them after every election, and they're almost gone. The more party unity there is, the more every race is nationalized.

So a message like, "I don't agree with my party's leader, even though I will sometimes, but not at other times, and I agree with you that he's a jerk" is going to be less persuasive now than it might have been at another time.

This could be especially tricky for the Republican incumbents representing swing states. We often think of "purple" states as containing mostly moderate voters, but that's often not the case. Instead, they may have roughly equal numbers of strong liberals and strong conservatives. You can see that in places like Iowa and Wisconsin, both of which will have incumbent Republican senators facing serious challenges this year. That makes things complicated for those Republicans — they don't want to alienate the Trump fans who will be coming out to vote for president, but they also don't want to push away voters who can't stand him.

And you can bet that in nearly every competitive Senate race, there are going to be ads targeting the Republican that will try to tie him or her to the Republican presidential nominee, particularly if Trump's popularity stays as low as it is now. "Senator X stands with Trump," they'll say, as sinister music plays in the background. "Demeaning women. Threatening immigrants. Encouraging violence. Is that what we want representing us? Tell Senator X and Donald Trump that our state says no thanks."

Some Republican incumbents are running in extremely conservative states, in which case they probably don't have to worry. But others will face two questions: Whether they even want to distance themselves from Trump, and if they do, whether they can do it successfully. One thing's for sure: it isn't going to be as easy as Mitch McConnell would have you believe. And the farther you go down the ballot, the harder it's going to get.