What Arthur Balfour once said of a young Winston Churchill is also true of Senator Elizabeth Warren.

“The right honorable gentleman’s artillery is very powerful but not very mobile,’’ Balfour said, taunting the eloquent speechifier about his inability to think on his feet.

We’ve seen the same from Warren recently. First, the power: Our senior senator delivered a blistering takedown of GOP front-runner Donald Trump earlier this week, blowing holes in his supposed business acumen, calling him out for his “petty bullying, attacks on women, cheap racism, and flagrant narcissism,’’ and his “embarrassing insecurities.’’

How wistful her cutting observations must have made those who had hoped Warren would run for president this year. In a way, her potential as a presidential candidate seems greater now than it did last year, when supporters tried to draft her. She speaks so beautifully to the disaffection that is driving middle- and working-class voters to Democrat Bernie Sanders (and Trump).

Now to that lack of mobility.

For an example, look to Warren’s disastrous interview on “CBS This Morning’’ last week. There, she spent almost five excruciating minutes ducking questions on whether she supports Supreme Court nominee Merrick Garland and avoiding saying when, or whom, she will endorse in the Democratic primary. Instead, she relentlessly focused on her talking points, on the shortcomings of the Republicans who refuse to give Garland a hearing, and on the lowness of the debate among GOP presidential candidates.

Look, it’s understandable that Warren wouldn’t want to give a full-throated endorsement to Garland until she meets with him. And she’s in a tough spot on an endorsement. Sanders more closely reflects her views, but Hillary Clinton is more likely to be the nominee, and Warren is clearly loath to say anything that could be used in an attack ad. But it wouldn’t have killed her to say: “Garland seems very impressive, but I’d like to meet with him before I make a final decision.’’ Or: “We have two great candidates, and I’ll support the nominee wholeheartedly.’’

However, the worst moment in that interview came when Warren was asked if she believes Clinton should release the transcripts of her paid speeches at Goldman Sachs.

“I think that our candidates are out doing what they should do in a primary,’’ she said. Challenged twice by host Norah O’Donnell, Warren repeated that mantra: “The primaries are doing exactly what they should be doing.’’

That was a monumental dodge for someone who has built a career on her fearlessness when it comes to Wall Street. Again and again, Warren has decried the coziness between politicians and bankers. It might have made her, and Clinton, uncomfortable, but there was only one answer for her to give to keep from seeming like a typical politician — and Warren didn’t give it.

The senator generally avoids being backed into such corners. In her few years in the Senate, Warren has often ducked reporters’ questions altogether — by being studiously distracted in hallways or simply fleeing. She didn’t even respond to a Globe query last week after a Missouri congressman compared her to Darth Vader and said she should be “neutered.’’ (Although she did express outrage in a fund-raising appeal the next day.)

Supporters might argue there’s something refreshing in her artlessness when it comes to eluding questions.

Maybe. But refreshing won’t take Warren very far if she’s inclined to higher office. Eventually, she will be required to be a more straightforward, and more nimble, stateswoman.

Perhaps she could take a lesson from Churchill, who worked hard to become an agile parliamentarian, practicing his ripostes until they came naturally.

History records it worked out pretty well for him.

Globe columnist Yvonne Abraham can be reached at yvonne.abraham@globe.com.