Yes, I know Pennsylvania Democrats don’t have a 2016 Senate candidate who excites the entire party yet. I also know the election is 20 months away — plenty of time for them to rally around a nominee.

GOP Sen. Patrick J. Toomey’s re-election prospects in Pennsylvania next year depend to a large extent on the state’s political environment when voters go to the polls. If it is like 2010 or 2014, he is likely to win. If it’s like 2006 or 2008, he is likely to lose.

But if 2016 is a more normal year — or , if you prefer, a more neutral one — Toomey’s prospects will depend on the races he and his opponent run.

“When I first met Toomey during his 1998 race for Congress, I found him to be bright, articulate and extremely personable,” I wrote in May 2009, about a year and a half before the then-former representative defeated the Democratic nominee, Rep. Joe Sestak, in a tight Pennsylvania Senate election.

“He has been in and around politics and fundraising for more than a decade, and I don’t think anyone should dismiss him or his abilities out of hand. In fact, I can imagine circumstances under which he could win the Pennsylvania Senate race,” I continued cautiously.

Toomey was no sure thing back then, primarily because the political landscape (both in the state and nationally) looked terrible for Republicans in the spring of 2009.

President Barack Obama’s job approval stood at 61 percent in the April NBC News/Wall Street Journal poll, and a remarkable 43 percent of those polled in that survey said the country was headed in the right direction — a dramatic improvement from where it stood in the low and mid-teens during President George W. Bush’s last months.

A year later, circumstances had indeed changed. Voters had turned against the president. Obama’s job approval in the June 2010 NBC News/Wall Street Journal poll slipped to 45 percent, and only 29 percent said the country was headed in the right direction.

In the last survey before the election, conducted Oct. 28-30, 2010, Obama’s job approval also stood at 45 percent, though the percentage who said the country was headed in the right direction had inched up to a still unimpressive 31 percent.

Under those circumstances, perhaps it isn’t surprising Toomey eventually squeezed out a 2-point win over Sestak, a Philadelphia-area congressman and former naval admiral who ran to the left and suffered from an exaggerated sense of his own importance.

Still, Toomey’s uncomfortably narrow margin in the Republican wave year of 2010 can’t be ignored. Republican challenger Ron Johnson defeated Sen. Russ Feingold, D-Wis., by almost 5 points that year, and Republican Rep. Mark S. Kirk won an open Senate seat in reliably Democratic Illinois by almost 2.5 points.

Toomey, a former president of the Club for Growth, certainly is a true believer when it comes to conservative political theology on taxes and spending. But the Harvard-educated Republican doesn’t convey the unbridled zealotry (or carry the political baggage) that some of his conservative colleagues do.

And maybe even more important for a Keystone State Republican, Toomey doesn’t push hot-button social issues the way another conservative Pennsylvania Republican senator, Rick Santorum, did.

Toomey worked with Sen. Joe Manchin III, D-W.Va., to expand background checks on gun purchases, and his allies insist there is plenty more in his record to help him woo moderate and swing voters.

Moreover, the senator’s style is more Manhattan (where he once worked in investment banking) than Pittsburgh or Scranton, which could be an asset in the Philadelphia suburbs, a crucial area of the state that is increasingly difficult territory for Republican nominees.

But the polished Toomey, who represented Lehigh (Allentown) and Northampton (Bethlehem) counties in the House for three terms, is going to need to roll up big margins in central Pennsylvania and carry western Pennsylvania if he is going to win a second term.

Of course, the dynamics of a presidential year can’t be ignored by Republicans. The GOP presidential nominee hasn’t drawn as much as 47 percent of the vote in the Keystone State since 1988 (when George Bush carried it), so it is certainly possible the senator will have to run well ahead of the top of his party’s ticket to win a second term.

But while Toomey almost certainly will have a tough fight on his hands, he doesn’t need to rely on a miracle to survive.

He has shown himself to be politically savvy, and his campaign ended December 2014 with over $5.8 million in the bank. Given his past fundraising success (he raised more than $17 million for his 2010 race) and his ties to the Club for Growth, you can bet Toomey will have all of the money he needs to run a first-class operation.

Pennsylvania Democrats will need a capable nominee and at least a neutral political environment to deny Toomey a second term. Given the state’s fundamentals, and the closeness of the 2010 contest, it is certainly possible they can accomplish that.

But the burden of proof is on them — and on the person they eventually nominate.