For all the presidential buzz surrounding her last year, Sen. Elizabeth Warren (D-Mass.) has been relatively quiet during the actual campaign.

But every so often, it seems the GOP candidates say or do something the liberal firebrand just has to denounce, 140 characters at a time. Why she chooses certain moments of the race to chime in -- in a high-profile and surprisingly provocative way -- is unclear. But it is clear Warren's stirring up controversy for her own political benefit.

To wit: In March, Warren tweeted that Trump was a loser. Her tweets made a ripple but not huge news. Then, on Tuesday, we found something else that sets her off: Republicans running for president who talk about how difficult it is to run for president.

Her reaction to a Cruz email to supporters saying as much is getting a lot of attention. Warren saw the email and logged on to her campaign Twitter account to rip into him on the night of the New York primary. Ted Cruz "whining" was a common theme.

Like any talented politician, Warren used the moment to spotlight her policy initiatives -- paid sick leave, affordable college, raising the minimum wage. Her bullish advocacy for them has made her a darling on the left.

In all, she sent a dozen tweets relentlessly going after Cruz and, really, using him to elevate her causes.

It's a safe bet Warren's tweetstorm won't actually hurt Cruz. The two operate in completely opposite political spheres. Anyone who likes what Warren has to say already dislikes very much what Cruz has to say, and vice-versa.

Which is why those tweets say more about her than Cruz. We don't know why Warren seized this moment, among the thousands of others this campaign, to inject herself into the presidential conversation; especially when she's successfully influenced the Democratic primary by laying low. But Warren clearly saw an opportunity here to champion her priorities at the expense of a Republican.

Or maybe she was just really, really annoyed by that email.