There is no more confounding presidential contender than Sen. Marco Rubio (R-Fla). When he is good, he is among the party’s stars, but when he is bad it is, well, painful.

Sen. Marco Rubio (R-Fla.) prepares to answer questions after delivering a keynote speech at Chatham House in London on Dec. 3, 2013. (Toby Melville/Reuters)

Starting with the positive, he speaks eloquently about the American dream and the immigrant experience. He understands and can articulate the need for bold U.S. leadership in the world. He speaks passionately about human rights. And he is one of the most effective exponents of reform conservatism.

Peter Wehner of the Ethics and Public Policy Center recounts a Rubio speech, co-hosted by Hillsdale College and the YG Network, last week:

The Florida senator offered ideas on how to reform our entitlement programs, tax code, higher education, health care, and our social safety net. In doing so, he spoke about single mothers and working class families, wage stagnation, student debt and retirement security, and the effects of globalization and automation. And like Representative Paul Ryan, Rubio understands the need for structural changes in programs, which is quite different, and rather more important than, simply reducing spending.

In making his case, Senator Rubio presented himself as an advocate for modernization rather than moderation (in this instance meaning nudging the GOP in a more liberal direction). He spoke about the need for a policy agenda designed for the 21st century and adjusting to the realities of this new era. Mr. Rubio clearly wants the GOP to be both conservative and constructive, opposing the president’s agenda but also willing to offer alternatives to it. The left, he says, is offering ideas that are old, tired and stale; a conservative agenda, as Rubio has laid it out, is innovative, responsive, and “applies the principles of our founding to the challenges and the opportunities facing Americans in their daily lives.”. . .

A friend of mine says he gets the sense from Rubio that he hasn’t spent his life in a political echo chamber, only hanging around like-minded individuals. He has the capacity, I think, to reach people who aren’t members of the NRA or the Federalist Society, the Tea Party or the American Conservative Union. The ability to find connection with people who aren’t already supporters is a fairly valuable skill in politics–and for a party that is regularly losing presidential elections, a necessary one.

And, of course, Rubio led the fight in the Senate for comprehensive immigration reform, showing real guts in going up against the noisy anti-immigration crowd.

All that is impressive. But then there is the “bad” Rubio. After taking hits from the far right on immigration reform, he virtually abandoned the issue and immediately plunged into the dumbest conservative stunt since impeachment of Bill Clinton – the government shutdown. It’s not clear whether he really believed this was a wise course of action or simply was trying to get back into the graces of the conservative right-wing base, but the gyration from immigration reform advocate to destructive shutdown squad leader left both sides dizzy and wondering who the real Rubio is.

To be blunt, at key times he has shown a distinct lack of political courage, an overeagerness to avoid offending voices that won’t ultimately support his presidential ambitions anyway. At every key budget juncture he has voted no, letting others in his party bear the responsibility for avoiding default or a tumble over the “fiscal cliff.” Despite his foreign policy inclinations, he opposed the authorization for use of force against Syria, thereby contributing to one of the most disastrous foreign policy episodes in recent memory. He again played up to the far right by opposing Ukraine aid (although he was absent from the vote), adopting a cockeyed justification that put him in sync with the right-wing opponents of international aid.

All of this leaves even Rubio’s admirers with questions about his maturity and resolve. Is he a thoughtful leader or a nice young man trying too hard to gain acceptance no matter what the cost to his own intellectual integrity? Is he in control of his own destiny or at the whim of ambitious staff that consider him their ticket to the White House? It is hard to say. And one wonders about his toughness and ability to project toughness. (I’m reminded of the young John F. Kennedy who failed to impress Nikita Khrushchev at the summit in Vienna, thereby encouraging the latter to risk installing missiles in Cuba.)

Fairly or not, Rubio is also hindered by the Barack Obama factor. Obama was the junior U.S. senator from a big state and the eloquent rising freshman star of his party, but someone who lacked executive skill and governing chops. Things worked out poorly, and more than ever before voters may turn a jaundiced eye toward another ambitious young man – at least until he has demonstrated that he can do more than give great speeches.

Rubio faces a choice for 2016 – run for reelection, run for president or, I suppose, do neither. Looming in the background, of course, is Jeb Bush, an early supporter of his career and fellow Floridian, who if he runs is likely to sweep up most of the in-state donors and the national, mainstream GOP money and support. If Bush runs, Rubio’s chances of winning the nomination surely diminish. Even if Bush stays out, the risk of an early loss for Rubio and a premature end to a promising career should give him pause. (Even reelection is no slam dunk, especially if the top of the ticket is weak). He has already said he wouldn’t run for both the Senate and the GOP nomination.

Because Rubio is so promising and so talented, some Republicans no doubt would like him to stay in the Senate, continue to lead on foreign and domestic policy and take time to settle down and gain confidence in his own judgment. That may not be satisfying to him or to his supporters, but it might be the best course for him, his party and the country. (And like Rep. Paul Ryan in 2012, a VP run might be in the offing if he doesn’t run for the top of the ticket.) In any event, Rubio will have six months or so to decide what he wants to do — and which Rubio he wants to be.