Being an incumbent ain't what it used to be.
Texan John Cornyn is the number two man in Senate GOP leadership and by most measures holds high conservative ratings — according to National Journal's rankings, he was the second most conservative senator in the last Congress.
But this week, Cornyn joined the crowded ranks of incumbent Senate Republicans who are now facing a primary challenge.
"The unhappiness people have with government opens the door to any challenger," says Michael Berlanga, a former GOP legislative aide in Texas. "Any incumbent needs to be on guard."
That may be particularly true in Texas. Just last year, Ted Cruz came out of seemingly nowhere to beat Lt. Gov. David Dewhurst, his better-known and better-funded opponent, in the Republican Senate primary.
"Everyone in the Republican Party is running on the Ted Cruz model," says Trey Martinez Fischer, a Democratic state representative. "You have to give credit to a winning model."