Piggybacking off yesterday’s post from Canadian Cincinnatus on hotly-contested US Senate races, Senator Mark Kirk of Illinois faces a formidable challenger in Congresswoman Tammy Duckworth. Kirk squeaked by in 2010, helped by a contentious race for governor at the top of the ballot. Even though the gubernatorial election was lost, Kirk received enough help from it to carry him to his first victory, though in a squeaker: he won 1,779,000 votes to his opponent’s 1,719,000 (the gubernatorial election was similarly close). And let’s recall that 2010 was a good year for Republicans.

Let’s jump ahead to 2014. In the governor’s race that year, we had a much stronger Republican, Bruce Rauner, who won a slightly-more-comfortable victory with 1,823,627 votes to the Democratic incumbent’s 1,681,343. But while Rauner has been fighting for deep structural reforms to the state government, Kirk has been working against conservatives and Republicans in Washington. Kirk thinks his victory in 2010 and Rauner’s in 2014 means he can do well this year, but Rauner’s attention and resources have been spent elsewhere, and the governor has generally been quiet about the US Senate race. It’s not without reason.

Turing to this year’s Senate primary results, Rep. Duckworth received 1,220,128 votes in a three-way race where 1,859,257 were cast. Kirk, meanwhile, faced a single challenger (whose name I had never seen until I voted) and won only 931,619 votes (70 percent) out of 1,320,190 cast. Kirk’s votes look even less impressive when you compare it to those in the presidential primaries held on the same day. Short version: Of the Republicans who showed up to vote on primary day, only 65 percent voted to re-nominate for their incumbent senator to retain his seat.