After breaking a promise to tackle immigration reform in his first year in office, President Barack Obama now thinks the time has come to deal with the thorny issue “once and for all.” It’s a safe bet that he will fail to repair America’s broken immigration system. Why? George W. Bush helps explain.

The immigration reform Bush championed would have provided tighter control over the 2,000-mile border with Mexico, a new visa system for temporary workers, and a path to legal status for millions of illegal immigrants already in the country. The bill failed in 2007 after running into stiff opposition from congressional leaders of his own Republican party.

In his memoir, Decision Points, he says the debate over the reform had been affected by “a blend of isolationism, protectionism and nativism,” apocalyptic warnings of a “third world invasion and conquest of America” by TV radio hosts and commentators and last but not least the influence of ideological extremes in Congress.

“The failure of immigration reform points out larger concerns about the direction of our politics,” Bush writes in a perceptive passage. Since members of Congress in safe districts do not have to worry about challenges from the opposition party, their greatest vulnerability is getting outflanked in their own party. The result is a drift towards the extreme, he writes, and “this is especially true in the era of bloggers, who make national targets out of politicians they deem ideologically impure.”

That trend was obvious in the 2010 mid-term elections that gave Republicans a 49-seat majority in the House of Representatives and brought in many extremely vocal guardians of ideological purity, adherents to the populist tea party movement.