Those out to halt Hillary Clinton's charge need a smoking gun
If imitation is the sincerest form of flattery, then constant vilification is conclusive proof of terror. So it is with Hillary Clinton and the Republican party.
The latter's primary concern right now is not to harass the Obama administration, or even complete its takeover of Congress in November's mid-term elections; it is to prevent Hillary Clinton from winning the 2016 presidential election.
First, we had Rand Paul, a likely Republican White House contender in 2016, raising the spectre of Monica Lewinsky.
Then, quite pointlessly, the Republican leadership on Capitol Hill decided to hold hearings into the 2012 attack on the US consulate in Benghazi, in which four American diplomats were killed.
Pointless in that the tragic incident has already been picked over a thousand times – but not if you want to embarrass the woman who was secretary of state at the time.
But these ploys seem positively gentlemanly compared with the suggestion by Karl Rove, George W Bush's old Svengali, that Clinton might be disqualified from the Oval Office because of "traumatic" brain damage caused by concussion during a fall at her home in December 2012.
The insinuations hark back to the tactics used by Lee Atwater, Rove's late friend and mentor in the political dark arts who was the top campaign gun for both Ronald Reagan.
Infamously, Atwater once let it be known that a Democratic opponent of one of his clients had been treated for depression in his youth, when he was "hooked up to jumper cables".
Made more politely, Rove's point now would be perfectly legitimate.
Presidents and would-be presidents haven't always been frank about their health.
Back in 1893, Grover Cleveland disappeared from Washington on a "fishing trip", only for it to transpire that he had spent five days on a friend's yacht undergoing cancer surgery; JFK would probably never have been elected had Americans been told of his incurable Addison's disease.
Today, the health of presidential candidates is minutely scrutinised. Clinton will be no exception.
For one thing, were she to run and win in 2016, she would be the second oldest incoming president in US history, after Reagan.
And even now, there seem discrepancies in accounts of the aftermath of the December 2012 fall.
But one thing is clear: it's looking more likely than ever that Clinton will, indeed, keep her date with history two years hence. The polls make her a favourite, while a campaign organisation and an unequalled money machine, is effectively in place, waiting only for the starter's gun.
After a long absence, the woman herself is doing fundraisers for other Democratic candidates, acquiring goodwill chits to be cashed in should she decide to run.
Nothing in politics is certain; just consider the untested neophyte, a year or two out of the Illinois state legislature, who upset the Clinton apple cart in 2008.
This time, however, there's no obvious Barack Obama in sight, though a challenger from the Democrats' liberal wing could yet emerge.
And after Obama, voters will be looking less for charismatic newcomers than for experience – precisely what she offers.
If Republicans want to stop Clinton, they'd better find something truly new and truly scandalous.