Delegates to the political conventions in Denver this week and St. Paul next week will have much in common each time they switch on an electric light or power up the laptop: The electricity will be generated by wind and solar power, and provided by Xcel Energy.

But the two men who will head the Democratic and Republican tickets have sharply differing views on another energy source, one whose farmer-producers could hold sway in the Midwest in the November elections. 
 
Democrat Barack Obama strongly supports federal subsidies for corn ethanol, which has been reviled by consumers as causing higher food prices, by humanitarian activists as contributing to worldwide food shortages, by environmentalists as an ecological disaster, and by clean energy advocates as contributing to the atmospheric carbon linked to global warming.

Most critics of corn ethanol tend to be likely Obama voters. 
 
Republican John McCain opposes subsidies for the biofuel, and he isn't shy about saying so. The Arizona senator recently told an audience in Des Moines — the capital of the state considered the nation's top corn and ethanol producer — that he'd stop the massive federal subsidies that give corn ethanol its commercial life. 
 
Yet most producers of corn and ethanol tend to be likely McCain voters. 
 
Bucking their constituencies
And how it came about that the two are bucking their constituencies on corn ethanol is a study in U.S. politics. 
 
McCain, seeking to burnish his conservative credentials, says he's generally opposed to government subsidies. In addition to opposing production payments, McCain voted against the 2008 Farm Bill, which extended taxpayer support to a long list of growers of agricultural commodities, and he voted against the 2007 Energy Bill, which included $21 billion in taxpayer support for the oil industry (a position he shared with Obama's vice-presidential pick, Sen. Joe Biden of Delaware). 
 
Obama supported the Energy Bill because, he said, it included support for ethanol.
 
Despite his campaign's reformer theme, Obama has sided with corn ethanol advocates at nearly every turn. 
 
Where he comes from — as well as the power of farm politics — might explain why. 
 
Obama is from Illinois, and so is Archer Daniels Midland of Decatur, Ill., whose founder, Dwayne Andreas, amassed a fortune by selling corn, soybeans and wheat. Andreas is also credited with successfully lobbying of such political stalwarts as former Sen. Bob Dole of Kansas and Minnesota's Hubert H. Humphrey to establish the taxpayer largesse that was to become the financial foundation for corn ethanol. 
 
Downstate Illinois is about Archer Daniels, agriculture, corn and ethanol, so much so that even liberal Illinois Sen. Dick Durbin, an Obama mentor, is among the vocal Congressional supporters of ethanol. 
 
Friends in farm country
Then there's Iowa, home of the nation's first caucus and where Obama was competing against New York Sen. Hillary Rodham Clinton, who at the time was expected to win both the state and the nomination. Corn is king in Iowa, and so is ethanol, so much so that Iowa's Democratic Party chair said you can't compete in Iowa and oppose ethanol. Obama and Clinton heeded the advice.

Further, McCain didn't win Iowa's Republican caucuses — Mitt Romney did.
 
Also, Iowa's liberal Democrat, Sen. Tom Harkin, is chair of the Senate Agriculture Committee. Both he and conservative Republican Sen. Charles Grassley support ethanol subsidies. 
 
Ethanol has a powerful friend in the Obama campaign. Former South Dakota Sen. Tom Daschle occupies a senior position in Obama's campaign, and he's also a senior adviser to several ethanol companies (he sits on the boards of three of them). 
 
In Minnesota, the divide between Obama and McCain on corn ethanol is being noticed in corn country. 
 
State Rep. Al Juhnke, DFL-Willmar, said he and U.S. Rep. Collin Peterson of Detroit Lakes — both ethanol supporters — are reminding corn and soybean producers of McCain's position. In Washington, Peterson is chairman of the House Agriculture Committee. 
 
"John McCain not only opposes ethanol subsidies but he voted against the 2008 Farm Bill, and farmers are hearing that," Juhnke said. 
 
The political "L" that covers the sweep along Minnesota's western and southern flatland region is quilted in agricultural crops including wheat, soybeans, and corn, corn, corn. It's also traditionally conservative and Republican, but how those farmers and their allies vote this year could be affected by McCain's strong opposition to, and Obama's strong support for, corn ethanol subsidies.