The southern German region of 12.5 million is a wealthy high-tech and industrial center, home to companies such as BMW, Siemens and Allianz. It has an unemployment rate of just 3.8 percent the lowest of any German state, and well below the already-healthy national rate of 6.8 percent.
"Germans are doing better than people in most other countries on this Earth, and you'll understand if we say that Germany is doing well and Bavaria is doing a little bit better," Seehofer said recently.
As Merkel looks to a strong showing in Bavaria for support, her center-left challenger, Peer Steinbrueck, has been downplaying the vote's significance, insisting that "the federal election isn't being decided here."
His Social Democrats fielded well-known Munich Mayor Christian Ude as their candidate for governor, but prospects look poor for his hopes of ousting the CSU in a several-party alliance and his personal ratings trail Seehofer's badly.
Steinbrueck argues that people often vote differently in federal and state elections, and says the outcome "won't change anything" in his party's national election campaign.
Manfred Guellner, the head of the Forsa polling agency, also is skeptical that the outcome in Bavaria will have more than a "minimal" impact on the national vote.
Merkel is heavily favored to emerge from the Sept. 22 national election with a third four-year term. Polls show Merkel's conservative bloc of her Christian Democrats and the Bavaria-only CSU leading the pack though not by the 25-point margin or more the CSU enjoys in Bavaria.
However, they show her current center-right coalition roughly level with the combined opposition, with a lead of up to about 10 points over Steinbrueck's hoped-for alliance of his Social Democrats and the Greens. That suggests she may need a new coalition partner.
One potential problem is the weakness of the pro-market Free Democrats, Merkel's junior governing partner. In national polls, they're hovering around or just above the 5 percent support needed to win seats in Parliament; in Bavaria, they've been polling below that mark.
Seehofer, like Merkel, runs a coalition with the Free Democrats. Unlike her, he'd be happy to dump them and govern Bavaria alone as his party did for nearly a half-century until 2008. Post-World War II Germany has never had a single-party national government, but they were long a matter of course in socially conservative Bavaria.
Top Free Democrat Rainer Bruederle argues that his party has been a useful "corrective" to the CSU and told Focus magazine this week: "Horst Seehofer must not be allowed to govern alone."
Seehofer has a populist touch and, like previous CSU leaders, often enjoys needling Merkel's party.
In this campaign, Seehofer has advocated a highway toll for foreign car drivers, which Merkel rules out. In the past, his party has talked particularly tough on Greece and other eurozone debt strugglers, and forced through to some allies' annoyance a new benefit program for stay-at-home parents.
Guellner noted the CSU has a tradition of attracting voters from the right to the center-left.
"Over decades, the CSU succeeded in creating an identity, (that) Bavaria and the CSU were one entity," he said.
Meantime, Steinbrueck's Social Democrats are simply "nonexistent" in much of the state, he said.
