THE REPUBLICAN Party of 2012, as captured in a poll by The Post and the Kaiser Family Foundation, has shifted significantly to the right on several key measures. One striking example noted by The Post’s Dan Balz and Jon Cohen: The share of Republicans who believe strongly that the government controls too much of daily life rose to 63 percent, up 24 points from a 1998 survey.

The challenge for Republicans is that they have not been willing to match their anti-government rhetoric with a realistic — that is to say, politically palatable — vision of what a smaller government would entail. Or, more to the point, what it wouldn’t: Presumptive nominee Mitt Romney, his running mate, Rep. Paul Ryan (Wis.), and others rail about waste and vow to impose tight spending targets but do not specify, beyond a few small tokens, which programs would be jettisoned or pruned. Nor have Republicans been willing to explain how they would pay even for the shrunken government they envision. Their tax policy blends magical thinking about the economic impact of tax cuts with fill-in-the-blank gaps where difficult, and politically perilous, policy choices would be.

Mr. Romney’s choice of Mr. Ryan, and the consequent focus on entitlement reform, offer the GOP a chance to present itself as the party of fiscally responsible grown-ups. Mr. Ryan’s carefully designed “premium support” model for Medicare reform is worthy of debate, and given the inevitable Mediscare campaign Mr. Romney deserves credit for advancing it. But peddling the illusion of pain-free tax cuts is irresponsible. So is the notion that the safety net the GOP ticket professes to want to maintain, the aging society’s health care the candidates vow to protect and the defense budget they insist must increase can all be paid for on a shrunken revenue base.

Then there are the social issues once again swirling around Republicans, as welcomed by party leaders at the convention as Tropical Storm Isaac. Leaders denounced Missouri Senate candidate Todd Akin’s ignorant and insulting remarks about abortion and rape. But Mr. Akin’s outburst reminded voters — not the overwhelmingly anti-abortion partisans attending the event but the ambivalent ones observing from afar — about the GOP’s outlier views on abortion rights. The party platform again calls for a constitutional amendment to prohibit abortion, with no exception in cases of rape and incest; this is a position opposed by the overwhelming majority of Americans. Mr. Romney would retain exceptions in situations of rape, incest and where the mother’s life is threatened; Mr. Ryan, who once took a no-exceptions view, says that the nominee’s stance is a good “first step.” But an unpopular one: In the Post poll, 70 percent of Democrats, 58 percent of independents and 34 percent of Republicans said abortion should be legal in all or most cases.

Other social issues, particularly combined with demographic shifts, also pose problems for the party. Its unyielding stance on immigration makes it difficult for the party to make inroads among the growing population of Latino voters. Its opposition to same-sex marriage conflicts with the drift of public opinion, particularly among younger voters. One final set of numbers from the Post poll underscores the peril for the party as its convention begins: The share of independents who believe Republican leaders are taking the party in the right direction has plummeted from 73 percent in 2005 to 28 percent today. That suggests some trouble with the GOP’s current definition.