John Cornyn — or whoever runs his Twitter account — is on a roll.

The Texas Republican senator was recently heckled by someone who called Cornyn a "RINO" — Republican in name only, for the uninitiated — and suggested Tea Party conservative Katrina Pierson should have run against him.

"Did so great against Pete Sessions," Cornyn retorted. (Sessions, a nine-term Republican from Texas, defeated Pierson in the primary by a massive 64 percent to 36 percent.)

Pierson's fans protested, but Cornyn wasn't done yet. Faced with protests from the supporters of other defeated Tea Party candidates — a tally that now includes Matt Bevin, failed challenger to Senate Minority Leader Mitch McConnell — Cornyn tweeted this:


It's not hard to see Cornyn's point — conservatives should want the GOP to win, and should thus always support GOP candidates, even when they're aren't the most reliably or truly conservative.

But are true conservatives really required to vote for any GOP nominee in order to hold onto the conservative mantle?

Remember, Arlen Specter was elected to the Senate five times as a Republican before giving the Democrats a filibuster-proof majority in 2009. George W. Bush and Rick Santorum helped him beat back a competitive GOP primary challenger in 2004; six years later he lost the Democratic primary. Were Pennsylvania conservatives abandoning their duty if they ever failed to vote for Specter — a man who wound up turning on them?

This is hardly an isolated example. Charlie Crist ran against Republican Marco Rubio for Senate as an independent when it became clear he couldn't win the GOP primary in 2010. He is running against Florida's incumbent Republican Gov. Rick Scott as a Democrat now.

Jim Jeffords was elected as a Republican to the House six times and then the Senate three times before he flipped the upper chamber to Democratic control in 2001.

I bet plenty of conservatives and Republicans regretted voting the party line in all those previous elections.

Still, Cornyn's comments got me thinking: When do you owe your party your vote, and when do you place your conscience above the party label?

My earliest voting experiences were in Massachusetts, where just 13 percent of registered voters were Republicans. Many of these were RINOs.

I happily voted for Bill Weld, Paul Celucci, and Scott Brown — all moderates who supported legal abortion. Despite our deep disagreements, Weld for governor seemed a no-brainer. He was likely to cut taxes and nearly certain to halt tax increases. He wasn't going to do much to make abortion more available in Massachusetts — already a staunchly liberal state — compared to what his Democratic opponents would do.

Yet when Weld ran for Senate against John Kerry in 1996, the calculus changed somewhat. Yes, he would vote according to my wishes much more often than Kerry. He would also have a much bigger platform from which to lecture Republicans on abortion and other social issues.

Where Weld once seemed like someone who could pull Massachusetts marginally to the right, I now worried he might pull the national GOP marginally to the left. I was still planning on voting for Weld, until he criticized Clarence Thomas. He called Thomas a "disappointment" and said he "wouldn't vote for him on a bet."

So I decided I wouldn't vote for Weld. I went for a conservative third-party candidate instead.

Four years later, I was initially excited to vote for Republican Jack E. Robinson (yes, his real name) when he ran against Ted Kennedy. But he wasn't very conservative and turned out to be more than a little crazy. Another third-party conservative it was.

I was sorely tempted to vote third party for president that year. I didn't think George W. Bush was conservative enough. I liked Pat Buchanan. Howard Phillips was another right-wing third-party possibility.

But the election against Al Gore was very close. My inner John Cornyn told me if I didn't vote for Bush, I had no right to call myself a conservative or a Republican. Bush it was.

I was happy when there were some tax cuts here, anti-abortion initiatives there. I didn't like Bush's free-spending ways, but rallied behind him like most everyone else after the 9/11 terrorist attacks.

Then came the Iraq war. Buchanan opposed it. Phillips too. And so did I. But not the man I voted for out of partisanship.

I didn't vote for Bush again in 2004. Foreign policy turned me off of voting for John McCain. I only backed Mitt Romney once I was confident he'd lose. He seemed like a good anti-Obama protest vote.

I still say I am a Republican, because that's how I normally vote. I almost never vote for Democrats. But sometimes, as John F. Kennedy has been quoted as saying, party loyalty asks too much.