Senate Majority Leader Mitch McConnell’s persistent refusal to schedule House-passed legislation to limit gun purchases and curb Russian election interference has stirred as much long-term Democratic concern as short-term anger.

Their concern stems from fears McConnell may well be in position to keep erecting roadblocks if Democrats win the presidency in 2020, a role the Kentucky Republican has already said he would relish.

They have a good reason for that concern. Early analyses indicate the GOP is likely to retain the Senate next year, regardless of the presidential outcome. That’s a big reason for the recent pressure on prospective presidential also-rans from Colorado, Texas and Montana to challenge potentially vulnerable Republican senators instead.

That looks like a long shot. Past elections show the better way for Democrats to overturn Republican control would be a bigger-than-expected presidential victory tide that also sweeps in some Senate seats.

Meanwhile, that pressure — and some political realism — has bagged its first big success. Having abandoned his lagging presidential bid, former Colorado Gov. John Hickenlooper has entered his state’s Senate race against the most vulnerable Republican incumbent, Sen. Cory Gardner.

Recent polls showed Hickenlooper would be the favorite, in both the Democratic primary and the general election.

But Colorado already looked winnable for Democrats. Former Texas Rep. Beto O’Rourke or Montana Gov. Steve Bullock would do more to boost Democratic chances if they switched to Senate races.

O’Rourke is widely regarded as the strongest potential Democratic candidate against three-term Republican Sen. John Cornyn, shown in a recent Emerson College poll for The Dallas Morning News to have a lackluster 37% job approval. But O’Rourke reiterated last week he won’t run.

Bullock, twice elected governor in red Montana, is seen as the only Democrat with a chance against GOP Sen. Steve Daines. But he has repeatedly rebuffed that idea, declaring he has no interest in being a senator. He’s hardly unique.

Earlier, Stacy Abrams, who narrowly lost a race for governor of Georgia last year, rebuffed entreaties from Senate Democratic leader Chuck Schumer to challenge GOP Sen. David Perdue.

Both O’Rourke and Abrams might have feared a second high-profile loss would doom their still promising political careers. But serving in the Senate isn’t what it used to be a generation ago, when it had high-profile debates and votes on the most significant issues of the day. Both are rare in an era of partisan gridlock, and McConnell has concentrated on confirming judges and other officials, rather than scheduling legislation that most Republicans and President Donald Trump oppose.

With Texas and Montana likely off their prime target list, Democrats face an uphill effort to gain the three Senate seats they need if they win the presidency, meaning a Democratic vice president could break ties, or four if Trump is reelected.

Although 22 Republican Senate seats are up in 2020, compared with just 12 Democrats, only a handful are considered at risk.

The most vulnerable, besides Gardner, are Sens. Martha McSally of Arizona, who was appointed to the late John McCain’s seat after losing a 2018 bid for the state’s other seat, and Susan Collins of Maine, the most moderate member of an increasingly conservative GOP caucus.

McSally faces a strong challenge from former astronaut Mark Kelly, the husband of former Rep. Gabrielle Giffords. In Maine, polls show increasing disapproval of Collins after she voted to confirm Supreme Court Justice Brett Kavanaugh. She has not said if she will run again, and several Democrats are running, notably state House Speaker Sara Gideon.

Offsetting those possible Democratic gains is concern about the reelection chances of freshman Sen. Doug Jones in strongly Republican Alabama. He narrowly won a 2017 special election after the GOP nominated controversial former state Supreme Court Justice Roy Moore.

Both parties hope to put other Senate seats into play that don’t seem especially vulnerable now. The top GOP hope is Michigan, where John James, who ran a strong race in 2018, is challenging freshman Democratic Sen. Gary Peters.

The top dark horse Democratic prospect may be North Carolina, which has seen several close statewide elections in recent years. The most likely Democratic candidate against freshman Republican Thom Tillis is former state Sen. Cal Cunningham.

Other Democratic targets include Sens. Joni Ernst of Iowa and Perdue. And they have long-shot hopes that former Marine fighter pilot Amy McGrath, who narrowly lost a 2018 House race, can oust McConnell, who has low job approval numbers. But most analysts say it would take an unlikely anti-Trump landslide in red Kentucky.

Even if Democrats add the presidency and the Senate to their House majority, they’ll lack the 60 Senate votes needed to pass most legislation, meaning solid Republican resistance can block their initiatives.

That’s why Democratic front-runner Joe Biden keeps talking of his hope that a Trump defeat will prompt some Republicans to pursue a more independent course and consider bipartisan solutions.

But that remains more a hope than a likelihood.

Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News. Readers may write to him via email at: carl.p.leubsdorf@gmail.com.