In 1774 and 1775 he was president of the first and second Provincial Congresses respectively, and he shared with Samuel Adams the leadership of the Massachusetts Whigs in all the irregular measures preceding the War of American Independence.
When, in the third of the short parliaments held at Oxford the Whigs rode armed into the city, the nation decided that the future danger of a Roman Catholic succession was incomparably less than the immediate danger of another civil war.
A friend of Harley, the duke of Shrewsbury, was first appointed to office, and subsequently the great body of the Whigs were displaced by Tories, Harley being made chancellor of the exchequer and Henry St John secretary of state.
At the general election of 1841 the Whigs returned in a minority of seventy-six, and Lord Melbourne was defeated on the Address and resigned.
The definitive peace of Paris was signed on the 10th of February 1763, and a wholesale proscription of the Whigs was begun, the most insignificant adherents of the fallen party, including widows, menial servants and schoolboys, incurring the minister's mean vengeance.
She yielded, after a struggle, also to the appointment of Whigs to bishoprics, the most mortifying submission of all.
In 1843 he was elected to the national House of Representatives and there remained for ten years until his district was gerrymandered by the Whigs and he lost his seat.
In general Grattan supported the government for time after 1782, and in particular spoke and voted for the stringent coercive legislation rendered necessary by the Whiteboy outrages in 1785; but as the years passed without Pitt's personal favour towards parliamentary reform bearing fruit in legislation, he gravitated towards the opposition, agitated for commutation of tithes in Ireland, and supported the Whigs on the regency question in 1788.
The favour shown him by Marlborough did not deter Rivers from paying court to the Tories when it became evident that the Whig ascendancy was waning, and his appointment as constable of the Tower in 1710 on the recommendation of Harley and without Marlborough's knowledge was the first unmistakable intimation to the Whigs of their impending fall.
First, for many years the Free-Soilers gained strength; then in 1855 in an extraordinary party upheaval the Know-Nothings quite broke up Democratic, Free-Soil and Whig organizations; the FreeSoilers however captured the Know-Nothing organization and directed it to their own ends; and by their junction with the anti-slavery Whigs there was formed the Republican party.