In 2008, 35 percent of Texan Hispanics voted for the GOP. No exit polls were taken in Texas in 2012, but the national Hispanic GOP vote was only 27 percent — four points lower than the national Hispanic GOP vote in 2008. So, going off of limited data, and giving the GOP the benefit of the doubt, the Democrats would need to swing Texan Hispanic voters their way by between four and eight points.

And while Republicans like Mr. Norquist and Texas Gov. Rick Perry say that the Democrat’s goal is a pipe dream because of the Texas GOP’s differences from the national GOP, they would be well served by studying the case of former Massachusetts Sen. Scott Brown, who, despite a roundly liberal record on abortion and other social issues, was painted as part of a national, socially conservative machine by 2012 Democrats. Then-candidate Elizabeth Warren didn’t focus attacks on Mr. Brown for his quotes regarding abortion, for example — she instead ran ads attacking former Missouri Rep. Todd Akin’s quotes on abortion.

In the next Texas election, Texas Republicans should not expect to be spared attack ads highlighting Arizona Gov. Jan Brewer’s harsher immigration policies.

By making races national when convenient, both parties have discovered a winning strategy — and one that can overwhelm a single state’s party apparatus.