His opponents attacked his participation in the treaty negotiations as unconstitutional and brought impeachment proceedings against him, a measure that was narrowly defeated by a vote of 15 to 13 after a month-long investigation and the resignation of the lieutenant governor.

During his second term and following the panic of 1819, Jennings encountered financial problems, a situation exacerbated by his inability to keep up with his business interests and run the state government simultaneously.

Among the modern historians, Randy Mills places Jennings's importance between the two extremes, but agreed with Woolen's assessment that the state "owes him more than she can compute.

[27][29][n 4] Jennings and his supporters who opposed slavery wrote writing articles appearing in the Vincennes Western Sun newspaper attacking Harrison's administration, its pro-slavery sentiments, and aristocratic policies.

Jennings entered the race against Harrison's candidate, Thomas Randolph, the attorney general for the territory, and John Johnson, a Vincennes native who had the support of the antislavery group.

[37] During his first session in Congress, Jennings had a small portrait of himself made, which he later gave to Ann Gilmore Hay, the daughter of a prominent Charlestown politician, whom he had recently begun courting.

[46] Following his reelection to Congress in 1811, the couple returned to Washington, where she remained briefly, before traveling to Pennsylvania to live with Jennings's sister, Ann Mitchell, for the remainder of the session.

Following his triumph in the election, Jennings's and his anti-slavery allies were successful in enacting a legislative agenda that limited the territorial governor's authority and repealed an 1805 act regarding indentured service.

[40][56] In his first full term in Congress, Jennings stepped up his attacks on Harrison, accusing him of using his office for personal gain, of taking part in questionable land speculation deals, and needlessly raising tensions with the Native American tribes on the frontier.

[57] Jennings presented a congressional resolution that intended to reduce Harrison's authority to make political appointments and opposed his policy of purchasing lands from the Indians.

[61] Early in the war, Harrison was commissioned as a military general and dispatched to defend the frontier and invade Canada, which caused him to resign from his post as territorial governor in 1812.

[61][62] Prior to Harrison's resignation, Jennings and his allies moved quickly to take advantage of the situation and initiated efforts to weaken the governor's authority.

When Harrison's successor, Thomas Posey, was confirmed on March 3, 1813, Jennings's party in the territorial legislature had become entrenched and began to advance their request for statehood.

[67] During his third term in Congress, Jennings began advocating that statehood be granted to Indiana, but held off formally introducing legislation until the end of the War of 1812.

[76] The new state government, divided into legislative, executive, and judicial branches, gave the governor limited powers and concentrated authority in the hands of the Indiana General Assembly and county officials.

After Indianapolis became the site for the state's permanent capital in 1821 and new settlers arrived in the area, the Indiana General Assembly appropriated $100,000 (~$3.06 million in 2023) for new road construction and improvements to some of the more important routes, but it was considerably short of the amount needed.

In November 1823 the Indiana Supreme Court upheld the termination of the bank's charter and concluded that the First State Bank had "embezzled" $250,000 of federal deposits, issued more paper than it could redeem, had debt exceeding the limited allowed under its charter, established more branches than its capital and specie could support, paid shareholders large dividends, and took steps to dissolve without paying debts owed.

The Indiana General Assembly was forced to significantly depreciate the value of its bonds, harming the state's credit and making it difficult to secure new loans.

[5] During his tenure as governor, Jennings nominated three candidates to the Indiana Supreme Court: John Johnson, James Scott, and Jesse Lynch Holman.

[87][101] In late 1818, Jennings was appointed as a federal commissioner, along with Lewis Cass and Benjamin Parke, to negotiate a treaty with the Native Americans (Potawatomi, Wea, Miami, and Delaware), who lived in the northern and central parts of Indiana.

[113][114] Jennings's win by a three-to-one margin suggests he remained a popular politician and the state's voters were not overly concerned by attacks on the governor's character.

[116] One historian suggests that Jennings's financial situation may arisen from the expenses incurred during his political campaigns, his long-time service in state government, and being too busy to adequately manage his farm.

[124] In the regular election to fill the seat for Indiana's Second Congressional District, Jennings easily won, defeating James Scott by a wide margin.

[130] In the presidential election of 1824, American political parties organized around three candidates: Andrew Jackson running against John Quincy Adams and Henry Clay.

[134] In 1827, ceiling plaster from Jennings's Washington D.C. boarding room fell on his head, severely injuring him, and ill health limited his ability to visit his constituents,[50] but he continued to remain a popular politician in Indiana.

[136] During Jennings's final term in office House journals show that he introduced no legislation, was frequently not present to vote on matters, and only once delivered a speech.

[143] The state's early historians, William Wesley Woollen and Jacob Piatt Dunn Jr., wrote of Jennings in an almost mythical manner, focusing on the strong positive leadership he provided Indiana in its formative years.

[150] Carmony argued that Jennings's "intemperance and poverty, should not obscure his significant contributions as territorial delegate to Congress, president of the Corydon Constitutional Convention, first state governor, and congressman.

"[152] Modern historians, Howard Peckham, Randy Mills, Andrew R. L. Cayton, and Dorothy Riker, argue that Jennings's legacy may lie "somewhere between the two extremes" of Dunn's and Esarey's assessments.

[153] Jennings believed in popular democracy, opposed slavery, and despised aristocrats, especially William Henry Harrison, for "trampling on the rights of his fellow Americans.