ST. PAUL, Minn. (AP) - Garrison Keillor, host of public radio's "A Prairie Home Companion," has endorsed Democratic Sen. Barack Obama for president, the Obama campaign announced Sunday.

The best-selling author and humorist wrote a letter to Obama declaring his support for the Illinois senator two days before Minnesota holds its caucuses on Super Tuesday.

"I'm happy to support your candidacy, which is so full of promise for our country," Keillor wrote, according to excerpts provided by the campaign. "Seven years of a failed presidency is a depressing thing, and the country is pressing for a change and looking for someone with clear vision who is determined to break through the rhetorical logjam and find sensible ways to move our country forward. That's you, friend."

Keillor explained why he's a Democrat in his 2004 book, "Homegrown Democrat: A Few Plain Thoughts From the Heart of America." In it he described the Republican Party as "a gang of pirates."

Keillor's latest book, "Pontoon," is the fifth set in the fictional town of Lake Wobegon, a setting also used for homespun tales on his radio show, which draws 4 million listeners each week.

In his letter to Obama, Keillor said seeing Obama and his family in front of the nation's Capitol next January is a happy prospect that would "bring an end to a long sour chapter in our history."

"And of course it will be exciting to have a president who can speak with grace and power to the American people," Keillor wrote.

Brian Walton, spokesman for the Republican National Committee, took exception to Keillor's criticisms of President Bush. "No amount of endorsements can make up for Barack Obama's complete lack of experience or empty rhetoric," Walton said.

Obama visited Minnesota Saturday, speaking to a crowd of nearly 20,000 at the Target Center in downtown Minneapolis. A poll by Minnesota Public Radio and the Humphrey Institute released Thursday showed him trailing slightly with 33 percent to rival Hillary Clinton's 40 percent, but the gap was within the poll's 4.5 percent margin of error.

"I've been entertained and inspired by Garrison Keillor's work through the years," Obama said in a news release. "As president, I will wake up every day thinking about how I can help make life better in places like Lake Wobegon all across the country."