Bush said Tuesday that his son needs a stronger congressional majority to push his agenda through Congress, the Houston Chronicle reported.
Bush said he sought out Poe and offered his endorsement in the southeast Texas congressional race.
"I invited Ted to come here because of my respect for him," he said. "I know a lot about his conviction, leadership and strength of conviction."
Poe, a former Houston judge, is running in a newly-drawn district created by Texas Republicans to elect another member of their party to the U.S. House. Lampson and four other Texas Democrats were targeted in the redistricting.
Lampson said he was not surprised by the Bush endorsement, but he called it "a partisan move." He said he often supports the current president, including voting for the war in Iraq.
Last week, the former president endorsed Republican Rep. Pete Sessions in his battle in Dallas with Democratic Rep. Martin Frost, another of the Texas Democrats targeted by Republicans in last year's redistricting fight.