No one's as good at covering Congressional Republicans as Robert Costa, so if he says Ted Cruz is seriously considering a run for president, it must be true -- which is not to say that it makes sense, or that he would win.
Why is Cruz a longshot? He's a first-term senator (yes, yes, exceptions and rules, etc.). He's probably too conservative even to win a GOP primary, but particularly to win a general election: Even his backers portray him as a latter-day Barry Goldwater, only somehow able to win. In just a few short months, he has managed to consistently alienate even his Republican colleagues -- which, whatever you think of the merits of Senate courtesy, won't help in a primary campaign (although he's also vice chair of the National Republican Senatorial Committee). David Frum paints a damned-if-he-can-raise-money, damned-if-he-can't scenario. Cruz even ran behind Mitt Romney in Texas last year, when both won handily. It's too early to see how the immigration bill that Cruz opposes will pan out; some Republicans fear that if it fails, the party will do even worse with Latinos, though Cruz's surname might dull the blow.
But what won't prevent Cruz from becoming president is his place of birth. Cruz was born in Calgary, Canada, while his parents were living there. His father is now an American citizen, but was not at the time; his mother, however, was born in the United States.
Helpfully, the Congressional Research Service gathered all of the information relevant to Cruz's case a few years ago, at the height (nadir?) of Obama birtherism. In short, the Constitution says that the president must be a natural-born citizen. "The weight of scholarly legal and historical opinion appears to support the notion that 'natural born Citizen' means one who is entitled under the Constitution or laws of the United States to U.S. citizenship 'at birth' or 'by birth,' including any child born 'in' the United States, the children of United States citizens born abroad, and those born abroad of one citizen parents who has met U.S. residency requirements," the CRS's Jack Maskell wrote. So in short: Cruz is a citizen; Cruz is not naturalized; therefore Cruz is a natural-born citizen, and in any case his mother is a citizen. You can read the CRS memo at bottom; here's a much longer and more detailed 2011 version.
This isn't the first time someone has questioned a candidate's citizenship -- and not just on bogus, Kenyan grounds. There were questions about John McCain's citizenship, because he was born in the Panama Canal Zone when his father was stationed there in the Navy. George Romney was born in Mexico to American parents, but faced no serious challenges to his bona fides in his 1968 run for the GOP nomination, though a few diehards even questioned his son Mitt's qualifications in 2012. There are birthers for prospective 2012 Republican candidates Marco Rubio and Bobby Jindal, too. On the Democratic side, there's no ground for any questions about Hillary Clinton or Martin O'Malley. New York Governor Andrew Cuomo is lucky to have been born in the New York borough of Queens, rather than an adjoining borough; everyone knows Manhattan isn't real America, either.
Still, questioning candidates' Americanism is a veritable trend -- and it's one that the nation could stand to leave behind. While there are more immigrants in absolute numbers in the U.S. than ever before, immigrants actually make up a smaller share of the U.S. population than during the 1890-1920 immigration wave, Pew points out. Few questions arose about presidential candidates' citizenship in those days for a simple reason: They were all old white Protestant men.* The greater diversity of candidates in both parties, reflecting more political buy-in across the ethnic spectrum, should be cause for celebration. With non-Hispanic whites making up an ever-smaller portion of the population, perhaps these birther flare-ups are the death rattle of nativism.
* Though an astute reader notes that Chester Arthur, of Anglo-Irish descent, had his status challenged during his 1880 vice-presidential bid.