The phrase "a pledge to try" is correct and usable in written English.
You can use it when expressing a commitment or promise to make an effort towards something.
Example: "In our meeting, I made a pledge to try my best to improve our team's performance this quarter."
Alternatives: "a commitment to attempt" or "a promise to make an effort".
It is true that Mr. Obama did run on a pledge to try to rise above partisan divisions.
Mr. Romney, despite signing a similar plan into law in Massachusetts, has made a pledge to try to "repeal Obamacare" central to his presidential campaign.
"It [represents] a pledge to try and do better, an offering of respect to those no longer here, and an opportunity for other people to do the same".
— Philip Gourevitch * President Obama: It's honorable that you made a family pledge to try and have dinner with your family most nights.
President Obama: It's honorable that you made a family pledge to try and have dinner with your family most nights.
I'll remember that one candidate made a brief pledge to try to change this country's politics before succumbing to reality — and I'll hope that some day another candidate will try again.
But he made no commitment to hiring anyone from the Giuliani administration -- beyond a campaign pledge to try to persuade Police Commissioner Bernard B. Kerik to stay on -- and he would not answer whether he liked the idea of Mr. Giuliani taking charge of a proposed downtown redevelopment authority.
Last week, Kenya's leaders decided to scuttle efforts to set up a special tribunal for the organizers and financiers of the election violence, which killed more than 1,000 people, putting forward a vague pledge to try perpetrators within existing institutions instead.
That is why a year ago a social movement was launched called Action for Happiness whose members pledge to try to create the most happiness they can in the world around them and the least misery29.
I pledge to try to stick to her ideas, and the old ways, for a fortnight.
They were generally pleased with his pledge to try to improve things.
