"In this age, in this country, public sentiment is everything. With it, nothing can fail; against it, nothing can succeed. Whoever molds public sentiment goes deeper than he who enacts statutes, or pronounces judicial decisions." -- Abraham Lincoln
Considering how the Republicans would have opposed the Keystone Pipeline may provide an object lesson.
If, for some reason (say, e.g., if Obama were for it!), Republicans opposed the Keystone pipeline and Democrats favored it rather than conversely, they would attack it far differently and much more effectively than Democrats. Indeed, Republicans would have made those who proposed it wish they had never stuck their toes into the tar to begin with.
Democrats rank their arguments based upon their importance, for example the contribution to warming of the planet. They believe that the most important factor is the most politically effective.
Earth to Democrats: "It ain't." If you don't believe it, look at your last election results.
Republicans do not rank their policy talking points from the most important to the least. Instead, they find those that resonate at the most basic level, and that can be easily drummed into peoples' psyches.
Indeed, it does not matter how small a matter it is. Like PCR (the technique we use in the laboratory to amplify infinitesimal amounts of DNA to large quantities), Republicans can transform any concern, no matter how small or how tangential, into a cause célèbre. Before Cliven Bundy decided to tell us his views of "the negro," they were "PCR'ing" this scofflaw into a national hero.
For Keystone, they would have had a big one, eminent domain, with a known track-record of stirring emotions, a gift for any public relations strategy. In Kelo v City of New London (2005), the Supreme Court pissed off nearly everyone by ordering the transfer of property from one private owner (the smaller, poorer one) to another (the larger, wealthier one) on behalf of "economic development" claims that would be good for the city.
If Republicans had opposed Keystone, they would have resurrected all the animus triggered by Kelo, seizing the moral high-ground against "government-ordered theft of American property, on behalf of a foreign corporation". Warming, pollution, competing claims about job creation... none of those abstractions can compete.
Nor would they have to create much new messaging. Justice Sandra Day O'Connor's dissent in Kelo did it all for them:
Any property may now be taken for the benefit of another private party, but the fallout from this decision will not be random. The beneficiaries are likely to be those citizens with disproportionate influence and power in the political process, including large corporations and development firms.
To "PCR" this, they would have added the word "foreign", and their case against Keystone would be made, indeed vindicating Justice O'Connor's fears. They would have paid visits to the Kelo property, that is now reportedly an eyesore, providing additional visuals. And, of course, it would open the door to further attacks on the hated judiciary as the culprits.
Additionally, if Republicans opposed it, they would wonder aloud if gasoline prices might not rise in the midwest as currently "locked-in" oil would have an outlet.
With this context, all the other sins of Keystone would become inarguable: not just taking, but inevitably polluting our land, our water supply, and Americans not getting a single drop of oil from it; the small (at most less than one week's worth of jobs, most not permanent) benefit in jobs compared to the price paid in the egregiousness of the property taking (anyone who believes the oil companies are spending millions lobbying because they care about jobs should make a bid to Sarah Palin on a bridge she will sell you); the contribution to global warming whatever its magnitude... and so forth.
But first, to be effective on these matters, one needs public sentiment, as Lincoln said 150 years ago.
Returning to reality, one might ask why Democrats have not employed this strategy. First, they would never think of it. Second, if they did, they would "poll it", find little concern about it and thus drop it.
Republicans would likely not bother polling it, but, even if they did, they would use the results only as a baseline to measure how their public relations strategy has moved it. Even without Kelo, they would have understood its potency. With Kelo, and a foreign corporation to boot, they would have would passed the champagne before they began.
And that is but one illustration of why Democrats lose and Republicans win despite support for Democratic policies being very high.
President Obama is one of Abraham Lincoln's great admirers. But, he never took Lincoln's words about the importance of public sentiment to heart. Not "opinion", but "sentiment", i.e.,feelings, where intensity is the critical factor.